The III-V nitride-based compound semiconductor composed of 3B elements containing aluminum (Al), gallium (Ga) or indium (In) and 5B elements containing nitrogen (N) has a wide energy gap and can be used for manufacturing electronic components such as semiconductor laser diodes (LD), light emitting diodes (LED), detectors, and high frequency and high power transistors.
Currently, other than sapphire substrates and silicon substrates, a substrate more suitable for epitaxy growth of the III-V nitride-based compound semiconductor layer is still not available, a large lattice mismatch may occur between the III-V nitride-based compound semiconductor layer and the sapphire substrate or the silicon substrate, and this may cause dislocation to the epitaxial layer and deteriorate the performance of device using the semiconductor film structure. To improve the quality of the semiconductor film structure and decrease dislocation density there between, various technologies for improving the quality of epitaxial growth, such as low temperature buffer layer technology, layer insertion technology, and epitaxial laterally overgrowth (ELO) technology, are provided.
The conventional low temperature buffer layer technology and layer insertion technology both are characterized by the following steps. Firstly, a low temperature epitaxy growth is performed to form a low temperature buffer layer which is subsequently annealed at a high temperature, such that the low temperature buffer layer can have a lower nucleation density. Then, a second stage of high temperature epitaxy growth is performed on the annealed buffer layer. Although the nucleation density of the epitaxial layer can be largely reduced by these approaches, the epitaxial structure of the epitaxial layer still has a large dislocation density. As for the ELO technology, regular holes or protrusions should be firstly formed on the epitaxial growth surface using by etching process in order to block the lattice defects extending upwards during the subsequent epitaxy growth process. Relatively complicated manufacturing process is required. Furthermore, the critical dimension and the process window of the mask used in the ELO technology are micrometer scaled. Besides the ELO technology requires longer manufacturing time and higher manufacturing cost. Therefore the applying the ELO technology to form an epitaxial structure with a large area can be rather costly.
Therefore, it has become a prominent task to provide an advanced compound semiconductor film structure to resolve the problems encountered in prior art.